Soldiers facing a building full of bad guys can now toss in a grenade, drive it to their hiding spot and detonate the explosive all via remote control.

South Korean defense forces are using a new "smart grenade" built by Hanwha Corp. that turns hand-to-hand combat into a game of high-explosives hot potato.

The new device is part of a trend of lightweight, throwable robots that allow combat troops to peer over walls, climb stairs and kill enemies from a distance. These devices were on display last week at the 2011 AUVSI Conference in Washington, D.C., an event that showcased unmanned systems from miniature robotic stealth ships to hummingbird-shaped spy cameras.

One military official said this new class of robots is already saving lives in Afghanistan and Iraq.

"They are giving us eyes-on information in places we can't get to," said an official with the Robotic Systems Joint Projects Office, a Michigan-based Department of Defense unit that coordinates all robotic devices used by the Army and Marine Corps, who asked not to be identified.

"We're fighting an IED war," he said. "It's not so much combat as finding out where the explosives are."

The downside of small, lightweight throw-able robots is that they can't carry as many sensor packages, have smaller batteries and smaller range than the big rovers.

Hanwha's chief research engineer Min Su Park said his firm's new smart grenade is already in use by South Korean troops.

The 1 1/2-pound device looks like a small plastic barbell with two rotating rubber treads connected by a plastic body that houses a radio transmitter, small video camera and explosive charge.

The smart grenade fits inside a protective shell. The shells are launched by a standard rifle grenade and can travel up to 100 yards to reach its target. A video produced by Hanwha also shows people launching the smart grenade using a giant crossbow (perhaps to penetrate ancient walled cities).

The grenade lands, breaks apart from its shell, skitters across a cement floor and then starts moving around. Hanwha and other defense firms are trying to sell the device to U.S. and European military officials.

So, too, is the Bedford, Mass.-based iRobot Corp., which has developed a five-pound rover that looks like a metallic green Tonka truck with an antenna sticking out the top. The First Look 110 robot is undergoing field trials this fall in Afghanistan, said Tim Trainer, iRobot's vice president of operations.

"For us, the engineering question is how do we lighten the load?" Trainer said. "How do we get (troops) some kind of robotic technology in a platform them can easily carry both in volume and in weight."

Larger robotic rovers that are used for bomb disposal and other hazardous tasks have been built by iRobot, but the challenge was putting everything into a five-pound package that doesn't fall apart.

"We broke a lot of stuff in the process," he said.

The First Look got its coming-out party at the AUVSI conference, and is projected to cost between $10,000 to $15,000 each.

The Recon Scout Throwbot is even lighter, just over a pound, and is made of a titanium shell around a two-way radio control and HD video camera. Developed through a DARPA grant, and made by Minnesota-based Recon Robotics, the Scout Throwbot is being used by more than 230 law enforcement agencies (mostly SWAT teams), according to company CEO Alan Bignall. The Scout is operated by a joystick handset that also displays the video feed.

Trainer said the next frontier is autonomy: having robots clear minefields or dangerous rooms without using a joystick or controller. His firm is already developing a device that can map a room, then report back for more instructions.